Wireless networks have experienced increased development in the past decades. Two types of wireless networks are infrastructure-based wireless networks and ad hoc networks. An infrastructure-based wireless network typically includes a communication network with fixed and wired gateways. Many infrastructure-based wireless networks employ a mobile unit which communicates with a base station that is coupled to a wired network. The mobile unit can move geographically wile it is communicating over a wireless link to the fixed base station. When the mobile unit moves out of range of one base station, it may connect or perform a “handover” to a new base station and continue communicating with the wired network though the new base station.
In comparison to infrastructure-based wireless networks, such as cellular networks, or satellite networks, ad hoc networks are self-forming networks which can operate in the absence of any fixed infrastructure, and in some cases the ad hoc network is formed entirely of wireless nodes. An ad hoc network typically includes a number of geographically-distributed, potentially mobile units, sometimes referred to as “nodes,” which are wirelessly connected to each other by one or more links (e.g., radio frequency communication channels). The nodes can communicate with each other over a wireless media without the support of an infrastructure-based or wired network. Links or connections between nodes can change dynamically in an arbitrary manner as existing nodes leave or exit the ad hoc network.
Nodes in an ad hoc network can utilize a Request-to-Send (RTS)/Clear-to-Send (CTS) protocol to reduce frame collisions introduced by a hidden node problem. According to this protocol, a transmitter node wishing to send data can initiate the RTS/CTS protocol by transmitting a Request-to-Send (RTS) message. The RTS message can be a short frame (30 bytes) and may contain the duration of a CTS-Data-Ack exchange that may eventually follow. A receiver node replies with a Clear-to-Send (CTS) message. The CTS message can be a frame contains the remaining duration of the data-ACK exchange that may follow. Upon receipt of the CTS message the transmitter node begins transmission, and any other node receiving the CTS frame should refrain from sending data for a given time (solving the hidden node problem). The amount of time the node should wait before trying to get access to the medium is included in both the RTS message and the CTS message. Any other node receiving the RTS frame but not the CTS frame is permitted to transmit to other neighboring nodes (solving the exposed node problem). The RTS-CTS protocol was designed under the assumption that all nodes have the same transmission range.
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